Hiram d



H. D. CURRIER.l

RuNK cmcun.

APPLICATIUN FILED APR. 5,1915.

Jig?

@ma y HIRAM n. CURRIER, or CHICAGO, ILLINOIS, AssIGNon 'ro kELLoGC swITCIIBoARD & SUPPLY COMPANY, or CHICAGO, ILLINOIS, A CORPORATION or ILLINOIS.

TRUNK-CIRCUIT. Y

Specification of Letterslatent. Patented Jilne 10, 1919.`

g Application filed April 5, 1915.` Serial No. 19,168.

To all 'whom t may concer-n:

Be 1t known that I, HIRAM D. CURRIER, a citizen of the United States of America, re-

siding in Chicago, county of Cook, and State of Illinois, have invented'certain new and useful Improven'ients in Trunk-Circuits, of

which the following is a specification.

My invention relates to telephone systems and has more particularly to do with systems` employing two-way trunk circuits for use between two exchanges as betweena main and private branch exchange, and has for its object, a novel and improved system ofthe above type.

In systems of the above character a call originating at the main exchange will beV answered by a so-called A-operator, who upon finding that the wanted line terminates` at a diiferent operators position, as-at a private branch exchange operators position, extends the connection over a trunk line leading to the second exchange. Theoperator then presses a ringing key to operate the signaling device associated with the opthe receiver oI" theoperators set.- One of the objects of my invention is the provision of means for preventing the operative connection of the l?. B. X. operators link circuit with the trunk circuit while the operator at the main exchange is applying ringing current to 'the Atrunk circuit. Other 0by jects of my invention will be more particularly pointed out in the appended claims.

For a more complete understanding of my invention reference may be had to the accompanying drawing in which only sufcient apparatus is shown for connecting a calling subscriber at a main exchange with a called subscriber at a sub-exchange or at a private branch exchange. The connection as shown is (ompleted through the medium of the calling subscribers line equipment L, link circuit C, trunk circuit D, private branch exchange linkcircuit E and the line equipment L1 of the called subscribers line.

Referring now more in detail to the apparatus illustrated, the substation A may be'of anyV well-known or suitable type of common battery substation. The line circuit L comprises the line relay LR, line lamp S, cut-ofi relay CO and multiple jacks J. The substation B is similar to the substation A in all respects. The line circuit L1 is similar to the line circuit L except that only one jack' is shown connected to the line of the called subscriber. Y

The cord circuit C ymay be of any wellknown type and as shown, comprises an answering plug AP and a calling plug CP connected by the heavily marked conductors and having the condensers K and K1 interposed. Associatedv with the answering plug AP is the answering tip supervisory relay AT and the answering sleeve supervisory relay AS, the two supervisory relays controlling the circuit of the answering supervisory lamp AL. Associated with the calling plug Cl? is the calling tip supervisory relay CT andthe calling sleeve supervisory relay CS, the two relays controlling the cir,- cuit ofthe calling supervisoryilamp CL. At- O isshown an operators set adapted to be connected to the cord circuit through the medium of the operators listening key LK, The link circuit C is adapted to complete connections between local substations or for extending a-call from a local substation over the trunk circuit D to a subscriber at aprivate branch exchange or for completing a call initiated at private branch exchange and extended to the main exchange over the trunk circuit D.

. The trunk circuit D terminates in the j ack J2 at the operators position in the main exchange and in the jack J 3 at the operator-s board at the private branch exchange. Associated with the jack J 2 is a line relay LR2, line signal S2, and cut-offrelay CO2. rlhe line relay LR2 and line signal are for use when connections are extended from the private branch exchange to the main exchange. Associated with the jack J 3 is a double wound link control relay LC, alternating current relay AC and the line signal S3. These relays come into operation when connections are extended from the main eX- change to the priVat-e'branch exchange.

The pri vate branch exchange operators link circuit E comprises an answering plug APl callingfplug CP1. connected through the medium ol the heavily marked Vconductors and having condensers K2 and K3 interposed therein.V The answering tip' supervisory relay AT1' and the answering" sleeve supervisory relay AS1, are associated. with the answering end of the cord circuit E,

and control the circuit of theV answeringfsuper-visory lfainpAL1 ina well-known manner. Associated with the calledfendo the cord circuit is a calling tip supervisory relay CT;1 and acalling sleeve supervisory relay CS1, for controlling the operation of the callingsupervisory lamp CLR The operators set@1 is adaptedto be connected to the link circuit E through themediumlof the listeningkey LIQ.

Having described in general the appara- .tus employed inthe preferredembodiment orf my invention as herein illustrated, connection from -a calling to called subscriber Will now be describedin detail.

`Assuming now that` the subscriber at substation desired toinitiate acall, upon re# movinghisreceiver from the switch-hook,-

a circuitis closed through the llin'e rela-y LR:

The line relay LR, upon energizing. closes a circuit through Ythe line lamp S. The 0p'- craterl upon noting the glowing of the line lamp S insertes the answering plu-g AP of the link circuit C into the jack J I of the line 'circuit L .thusv closiiiga circuitthrougli the answering sleeve supervisory relay- ASand cut-01T relay C0. ,This circuit etends from battery through theVV Wiiiding of Athe said answering sleeve supeivisory rela-y AS,- V-sleeve coiiductor of the plirgAP and jack J and Winding of cut-oifrclay C0' to ground.`

The cute relayvCO, upon energizing, discoifi'nects theline relay BR from lthe subscribers liiie and" coinpletes coifinectioi'i be'- tweenthe conductors of the jack J a-nd'tlife subscriljierlsv line thus closing a circuit througli the answering tip' supervisory relay AT. The circuit for the answeriiig tip supervisory relay AT extendsfromi battery through the Winding of said relay ilk-S", sleeve conductor. of plug AP and jaek Jr, al# ternate Contact 3 of cut-oli relay CG, to and throughthesubstatioi'il A, a-l'teri'i-ate contact 2 of relay CO, tip? conductor of jack' 'J and lilug All and througlixthe Winding of ansiveriifig tip supervisory' relay AT to ground.` Relay AT, u'ponenergiz'lng, prevents the premature glowing of the an'- listeningl'ey Llto connect her' set O with* the li'ii'rk circu'it'G and inquires the ivants of the callingsubsciiber; Upon learning-that the cz'illilng subscriber desires connection with asubscriber a'tfthe -}lirivate-brancl`if exchange, the operator ilnfa'kes al preliminary busy test and' then inserts the calling plug CP into jack J2 of the trunk circuit D.

Uponl i insertion ot the 'callingfplug-CPV into jack J2, an energizing circuitis closed through cut-od relay CO2 associated Vwith jjack J 2., This circuit extendsfroinvbattery through the calling'sleeve supervisory relayGS`,sleeve conductor or plug CP Vand jaczk J V2-and the Winding of cut-off relay CO2:V

conductor Sufto'the private branch exchange thenthrou'gh' the condenser-2 K5, lower Winch ing oriv the link control relay LC,- Winding'of alternating current relayAC back overthe opposite trunk.conductor'T, through alternate contact 7v of cut-.oill relay CO2, sleeve conductor. of the jack J 2: andphrg GP and throughy the alternate contact ofringiiig key RK to-battery, back' toth'e'` grounded pole ofi generator: G. The link control relayiLG,

upon energizing,l disconnects the tip and Y sleevei'conductoi-'s ci:V the jack J3 from the trunk c'oiid-L'ictors by opening-its nor1n'aflf`=con tacts and' 10; and closesav lockingA circuit for itself at itsy a'lteri'iate Contact 1l independent of itsy original energizing circuit.

The l'ocking circuitior lin-kA control relay L@ extends from battery through theupper winding offsa-ifd relay, vits alternate Contact 1l,- contact llZ-ojfack J 3 to ground. ik. further result due to' the Venergizing off link control rely` LC is the: closing of a circuit through the line lamp'- S3, traced `from: (battery tliiouglr` theA said lamp S3, alteiuaateA mal contactlQv of j ack- J 3 to" ground. v

Theroperator at the private branch 'exchange ufp'en notingthe glowing of the line lam-p Si inserts-theanswering plug-MP1 of the link circuit E into the jlack J 3 of the trunk circuit. D. vUpon the insertion of the an-fsweringpluig A2P1 into' juck J 3,' the circuit of the link coirtrollrelay L@ is openedat norinail contact 112- 'of jack J3. However, it' ringingl current ifs1 bei-ng appl'fife'dtothe trunk izo conductors of the trunk circuit D, the alternating-curr'eiit relay VieCv'fill reina-in energizedyv as' ylonfg as current is'ib'eiifig! applied to the trunk circuitkover the h'ereinbefore tracedcircilit, and operates to prevent the link control relay L@ from dencrgizing anld connecting trunk conductors to the tip and sleeve conductors of the answering plug A131. The circuit io-rr'preveiiiting the :de-l

ll() coiitactfll. of link control relay LC, norf cnergizaition of Y the link control relay LC While fringing current is, fbeing applied to the trunk conductors, extends from battery through the vupperk winding of saidl relay LC, alternate contaot 11 of said relay and alternate contact 13.01 'alternating'.current relay AC to ground. i As soon,however, as the link control relay LC denergizes, a eircuit is established for answering sleeve supervisory relay AS1 and Yanswering tip sulpervisory relay AT1 of link circuit E. The circuit for answering sleeve supervisory relay AS1 extends from -battery through the winding of said relay AS1 sleeve conductor of plug AP1 and jack J1, norinal contact 9 of relay- LC, alternate contact 6 of relay CO2, tip conductor 'of jack J 2 and plug CP, alternate contact 14,01 relay CS and `through the calling tip supervisory rela-y CT `to ground. Thecirouit for the answering tip supervisory relay AT1 `extends from battery at link circuit C through the winding of calling sleevesupervisory relay CS, through the sleeve conductor of plug CP and jack J 2, alternate,contact. Tof cut-off relay CO2, normal contact 10 ofrelayLC, tip conductor of; the `iack J1" andplug AP1and through the winding of said ansuf'ering tipsupervisory yrelay AT1 to ground The energiaing of the answering tip supervisory relay AT1 prevents a preinat-ure glowing of answering supervisoryrelayAL1 while Vthe energization of `tip supervisory relay CT of link circuit C opens the circuit ofthe calling supervisory lamp CL and indicatesto the operator at link circuit C that the operator 1 atthe private branch exchange hasinserted y'the answering plug AP1 into the jack J3` of the trunk circuit D.4 `Theyoperator at link circuit. E now operates4 listening key LK1 to bridge her set O1' across the strands of the link circuit E. 1'-

The operator at the link circuit C or the subscriber at calling substation A,`as the case inay be, now informs the operator ot the link circuit E what local substation of the private branch exchange is desired. The

operator at the private branch exchange upon learning the number of the desired substation, makes a preliminary lousyv test, and assuming that the called line is idle, inserts the calling plug CP1A into the jack J1 of the called line. Upon the insertion of the calling plug CP1 into jack J1 an energizing circuit is closed for the cut-oi relay CO1 Iof` the called line, traced from battery through the winding of the calling sleeve,

supervisory relay CS1, sleeve conductor of the plug CP1 and jack -J 1 and through the winding of cuit-off relay CO1 to ground. The calling sleeve supervisory relay CS1, upon energizing, closes a circuit through the calling supervisory lamp CL1 at its Contact 1'?. Cut-off relay CO1 upon energizing, .disf

connects the line relay LR1: Afrom the line .tacts 18,- 19.

ot the. called subscriber'` and connects thc linesof the called subscriber to the strands of the cord cir-cuit D through alternate con- The yoperator now o-perates the ringing key VRK1 to connect ringing cui'- rent from generator G1 to the line of the calledsubstation. The circuit for the ringing current extends from the ungrounded pole of generator G1 through alternate contact of ringing key. RK1, tip conductor of calling plug CP1 and ack J1, alternate contact 19 of relay CO1 to and through the substation B, alternate contact 18 ot relay CO1, sleeveconductor of jack J1, and plug CP1 and alternate contact of ringing key RK1to battery, and through battery back Y cuit extends from battery through the calling sleeve supervisory relay CS1, sleeve condu-ctor, of the calling plug CP1 and )ack J1, alternate contact 18 of relay CO1, to and through substation B, alternate contact 19` of relay CO1, tip conductor of jack J1 and calling iplug CP1 and through the winding of the calling tip supervisory relay CT1 to ground. The calling tip supervisory relay, upon energizing, opens the circuit of the calling supervisory lainp CL1 at its contact 20, thus .indicating to the operator that the called subscriber has responded. The subscri'bers may now carry on conversation over the heavily marked conductors. Y i l Assuming that conversation is now terininated the calling subscriber, upon replacing his receiver, opens the circuit of the answering tip supervisory relay 4AT of link circuit C and thereby allows the saine to denergize. The answering tip supervisory relay AT, upon denergizing, closes a circuit for answering supervisory lamp AL..at its con-l tact 4. The called subscriber uponreplacing his receiver opens the circuit of the calling tip supervisory relay CT1 of link circuit E, at switch-hook contacts of the substation thereby allowing relay CT1 to denergize. The calling tip supervisory relay CT1, upon denergizing, closes a circuit through the calling supervisory lamp CL1, thus indieating to the operator at link circuit E that the called subscriber has replaced his receiver. The operator at link circuit E now removes the calling plug CP1 and answering plug AP1 from their respective jacks. The removal of the calling plug CP1 allows the cut-off relay CO1 of. line circuit L1 and calling supervisory relay CS1 to denergize and return to normal. The removal of the answering plug AP1 from jack J 3 of trunkcir-v l E in a well-known manner.

supervisory relay CT of link circuit C to deenergize and return to'normal. VThe calling tip supervisory relay CT, upon denergizii'ig, closes the circuit of calling supervisory lamp 'Y CLvof link circuit C at its normalcontact'Q The operator link circuit C iiponnotin'g the glowing of the answering supervisory lamp AL and calling supervisory lamp CL removes the answeringplug AP and the calling plug CP from their respective' jacks.

The removal of answering plug AP from jack J allows the' answering supervisory relay- AS and cut-olf relay CO to return to normal and the removal of the calling plug CP from jack J 2 of the trunk circuit D, allows the cut-oli" relay C()2 of trunk circuit- D to return to normal.

Assuming now that a subscriber at the pril vatev branch exchangev wishes tol communicate with a subscriber at the mainexchange, the subscriber at private branch exchange upon removing his receiver, causes the line signal S1 to glow in the same manner as described for the line signal S associated with the' line'- circuit L of substation A. The operator at the private branch exchange' now inserts. the answeringplug A131 into the jack J1 of the calling subscriber, operating the cut-on relay CO1' of the linecircuit L1 and answering sleeve supervisory relay AS1 of link circuitl The, operator now actuates listeningkey LK-1 to learn the wants of the calling subscriber. i Upon learningthat the wanted subscriber is' one whose line terminatesat the main exchange,` she in'- serts the calling plug CP1 into jack J 3 of the trunk circuit D. Uponth'el insertion' ofthe plugfCP1 into the jack J3,a circuit isj-close'd through line relay LR2 associated `witlrj-ack J2,traced-t1`'om` battery through the winding of said relay,- normal contact V7 of relay CO2, norm-al Contact 10 orelay LC, tip conduce tor of jack J 3 and plug CP1 andthrough' the calling-,tip supervisory relay CT1 toground.: Linerela-y LR1, upon energizing,` causes line lamp S2 to glow. The operator at thelm'ain exchange upon noting the glowing 'of the' line lamp' IS2, inserts the answering plugP of link circuit C into jack-J2 of trunk circuitD'.` The insertion of plu'gAP into jack .lf-closes a circuit through' the" cut-oil relayA CO2 ofthe trunk circuit D1 and the answering sleevev Vsupervisor-y relay AS' of linkicirou-it C in seriesf- This circuit extends fronr'battery `through winding of said answering' super-A visoryl relay AS', sleeve conductor of plug AP and jack J 2 and' throughout-or relay C02 to ground.- Thecut-otfrelay CO2, upon energizing, disconnects line relay LR2 froinf-4 the trunk circuit D an'd conn'ects'the cond-uctors of jack- J2 witlrthe strands ofther` trunk circuit thus closing a series circuit through the! calling tip' supervisory relayl CT1 of link circuit Ey and answering supervisory relay ASof link circuit C and' also closing! a series meager;

circuit/through lthecalling sleeve supervisory .Y i

relay CS1,-.the1link circuit E and answering tipsilpervisory reliay'Arll ofthe link circuit C: The former circu'itfextendsffrom battery throng-lrtlie: wi'ndin I oianswering sleeve supervisory' iel'iy-l Ab; sleeve conductors oliiV ai'iswveriirgplug andi jackl J 2, alternatecontact 7 o`flrelayfC2,normalcontactlOof Y Y relay. LC,- tip conductor' of` j ack J3' and ,plug- CP1 and-tlirou'gh:tlie winding of the calling` tip supervisory relay C111 oztlli'nk circuit E battery through the calling l sleeve supervs. sory relay CS1,P of link circuit' E,=sleeve' conductor opl'ug'CP1 jackJinormalfconta'ct 9;Tof'relayLC,alter1ratecontact 6 oi-relay CCLQtip conductor of jackJ1 andplug AP and ther winding of vthe answering tip supervisory relay" orfV link circuit` C to.v

ground@ rLhe' operatori at the' `link Y circuit C is now informed oit Ythe callingfsubscribers desiresand 4completes.th'e connection to the Y' linccfthe wantedJ subscriber'byinsertngitrre cal'lingfplug CPot-the" link circuit C into'th'e 'j ack p J ofi the" wanted f subscriber. c The' subscribers inayl now carry on conversation over-- the l'i'ea'f-vily marked conductors; :The calling subscriber upon replacmghis receiver causes the answering supervisoryflamp XL1 to glow ing subscriber'wanted connection Vwith a local private branch vexchange subscriber, the

operator at the private branch exchange lwould havey taken the"calling."plug CP1 of link circuit E' and inserted1 it into the jiack .of the' wanted subscriber-arid operatedthe ringing key; R'K1 to' signal the wanted subscriber. Thev operation of tl'i'ef apparatus inf establishing this cfnrn-ectionv is brafctical-ly the same' as hereinbefore' 'cl-escribedv- Y While I have illustrated'the preferred em# bodimentof my invention 'in certain specific circuit arrangemcnts,yet, itis to be underthe specific arrangemei'its shown as many changes airdf modifications will readilyv suggest themselves to oneskill'ed the art; and

modifications that comerwithi-n the contemplated spirit` and scope of the V.appended claims; l

Having `described my invention, what I therefore' I desi-re tocoverafl-l' changes and. K

i claim as new and desire to States Letters Patent, is

1. In a telephone system a trunk circuit provided with a pair o-f'terminals, connect-il i 'current to the other of said terminals, and

means for preventing the operative association ofthe said connecting means withV the said trunk vwhile ringing current 'is being applied.

2. A telephone system comprising a trunk circuit extending between two operators boards, a terminal at one of said boards -for connection to said trunk, means at the other of said boards for applying ringing current to the said trunln'and means for preventing the operative association of the said terminal being applied thereto.

3. In a telephone system an VA-'operators board and -a B-operators board, a trunk eir- -euit extending between said boa-rds, an

operators set associated with said'B-operators board, meansfat the A-operators board for applying ringing current tothe said trunk circuit, and means 4included inlthe said trunk circuit for preventingthe connection of said operators 'set to thesaid trunk while ringing currentis connected therewith.

4. In a telephone system an A-operators board and a B-operators board, 'an operators set at said B'board, atrunk circuit extending between theH 'said"boards, means at the A-operators board for applying ringing current to said trunk circuit, and means in` said trunk circuit for preventing the operative associating of the said operators set with the said trunk circuit while ringing current is being applied to the said trunk circuit.

5. In a telephone system a trunk line provided with a pair of terminals, connecting means for one end of said trunk circuit, means for applying ringing current associated with the opposite end of said circuit, and means in said trunk circuit for preventing the operative association of the said connecting means with the said trunk while the said ringing means is connected thereto.

6. In a telephone system atwo-way trunk circuit provided with a pair of terminals, connecting means associated with each of said terminals, means for preventing the operative association of the connecting means at one end of said trunk while a call is being signaled for from the opposite end thereof, and means for extending a call in either direction over the said trunk circuit.

7. In a telephone system a two-way trunk circuit provided with a pair of terminals and extending between an A board and a B board, means for applying ringing current to one terminal of seid trunk circuit and means at the cppesiteend of said trun i cirsecure by United cuit for preventing the ringing current from being connected to the other terminal of said trunk circuit, said means including a pair of relays responsive to ringingfcurrent, one of said relays being provided with a pair of 2 windings.

means at `the opposite end of said trunk circuit foi' vpreventing the ringing current from being'connected to the other terminal of said trunk circuit.

' 9. In a telephone system a trunk circuit provided with apair oi` terminals, connectn 'ing means'associated with one of said terl withthe said trunkwhile ringing current is ininals, ringing means associated with the other of said terminals, a relay responsive to `ringingcurrent vassociated with said trunk 4circuit for controlling the continuity of said .Y cuit, and a signaling battery adapted to be connected to one end of said trunk circuit to affect such disassociation. t

IL An inter-office trunk circuit extending between two operators7 switchboards, a signaling battery associated with one end oi said trunk circuit, and-ineans responsive to the connection of said signaling battery to said trunk circuit for disassociating the opposite end of said trunk circuit from said iirst end.

12. A trunk circuit extending between two operators boards and terminating in connecting terminals upon said boards, means for operatively disconnecting one of said terminals from the other, said means being responsive to signaling current connected with one end of said trunk circuit.

13. In a telephone system, the combination of a calling station, a called station, conductors connecting said stations, calling current generating means at the calling station, means to connect said current generating means to said conductors, a. telephone set at the called station, means to connect said telephone set to said conductors, and apparatus at the called station preventing the connection of the telephone set to said `conductors whilethe calling current is conf preventing the connection vo-said telephone set 'to said conductors While y'the calling current is connected to said conductors.

15. 'In a telephone system, the combination of a main exchange central station, a

private branch exchange central station, a,

telephone-set at the private-branch exchange central station, `a trunk circuit for connecting said stations together, means for enabling ythe mainexchange kcentral station operator to signal ,the `private branch AeX- `change central operator, including a source of calling current and means to apply said source lto the #trunk circuit, mechanism to ,connect the receiver of the telephone .set of the private branch exchange central sta.

`tion operator to the tru-nk circuit, and `means ,to prevent the conneetionof said receiver to --saidtrunk circuit during the application of -calling current from said .source to said trunk.

16. In a telephone system, the combination of a calling station, a called' station, .conductors for connecting said Vstations together, a source of .calling current (at the calling station, and means to connect it `-to said conductors, a telephone set at-the called l station including a telephonev receiver and Copies of this patent may'belpbtained for 1preventing y Signed Jayme Vat 1Chicago,,

meansfto .connect said-receiver to said iconductors, and apparatiis Icontrol-led by the Acalling 1 current to prevent the connection of lsaid `Itecei ver to i said conductorswhile vthe Icall-ing ,current Iis' f-connected toqsaid conductors. Y Y i f l 1f? A trunlrgci-rcuit n eXtending from one 'exchangetofanothen ajsource of signaling current, means-for I`ap,plyi-ng said Ysignaling .cnrren't tonne endof `said trunk circuit, and

means associated with said trunk circuit :for

traversing the terminal in v vhich the other end of said .trunk `circuit Ite-rminates, said last means being `controlled by said signal- -li-Hauri'ent- 18,. Altelephone system including a trunk 4ici rci1i t terminals in which said trunk cir- -cuit terminates, a 'sourceof signaling current, means for associating ,saidsoui'ce .of current with one. l`end of said: trunk ',cireuit,

current from' passing through .the vterminal the f:other end of 4,said trunk circuit, Vsaid last means keine controlled. la' Said signal- ,current said signaling `current from Y 

